The invention relates to a junction barrier Schottky diode and a method for manufacturing the same, and in particular, to a technique that is effectively applied to a semiconductor device represented by a liquid crystal display (LCD) driver or a complementary metal-oxide semiconductor (CMOS) integrated circuit.
A Schottky diode has a characteristic that the reverse current is large compared with that in a pn diode. The reverse current strongly depends on the electric field strength at the Schottky junction interface. As the electric field strength at the Schottky junction interface increases, the reverse current increases. In order to suppress the reverse current of the Schottky diode, for example, a known diode having a junction barrier Schottky (JBS) structure is used in which a p-type layer is formed in the anode region of an n-type layer of the Schottky diode and a pn junction is arranged in an alternating manner. The diode having a junction barrier Schottky structure (also simply referred to as a JBS diode) uses the spreading of a depletion layer of the pn junction in case that a reverse voltage is applied thereto. Since the electric field at the Schottky junction interface can be reduced by blocking an n-type semiconductor region bottom portion that is in contact with the silicide interface with the depletion layer, it is possible to suppress the reverse current. For example, FIG. 25 shows the schematic configuration of a vertical cross-section of the JBS diode when a forward voltage is applied thereto, and FIG. 26 shows the schematic configuration of a vertical cross-section of the JBS diode when a reverse voltage is applied thereto. When a forward voltage is applied, a depletion layer of the pn junction is not extended. Accordingly, current flows from the anode to the cathode. However, when a reverse voltage is applied, the depletion layer extending from the p-type layer is connected to another depletion layer of the adjacent p-type semiconductor region to block the side surface and the bottom surface of an n-type semiconductor region that is in Schottky contact therewith. Therefore, since it is possible to reduce the electric field at the Schottky junction interface, it is possible to suppress the reverse current. Since the size of the depletion layer depends on the applied reverse voltage, the size is determined by the power supply voltage to be used or the applied voltage.
An example of the JBS diode is disclosed in JP-A-2003-188391. In the JBS diode disclosed in JP-A-2003-188391, p-type layers within the anode are arranged at equal distances therebetween in rectangular shapes or arranged in a lattice shape. In particular, in the JBS diode disclosed in JP-A-2003-188391, in view of the fact that each p+-type semiconductor region arranged below the anode electrode is a so-called inactive semiconductor region that contributes to the reduction of reverse leakage current but does not function as a current path substantially during the forward operation, the depth of each of a plurality of p+-type semiconductor regions is set to be larger than the depth of an n-type epitaxial layer in order to form a Schottky junction region, so that the spreading of the p+-type semiconductor region in the horizontal direction when forming the p+-type semiconductor region by diffusion is limited to the n-type epitaxial layer. As a result, it is possible to prevent the occurrence of a situation where the area of the p+-type semiconductor region is undesirably increased and the required amount of forward current is not obtained.